alsa-project/alsa-lib issue #221 was edited from davidboulangerlatour:
I have an application which plays a wav file (using dshare) at with a specific period (ie. every 720ms). This always worked well up to recently after upgrading alsa-lib from 1.1.7 to 1.2.4. With 1.2.4, the cycles look like this [750ms, 750ms, 750ms, 625ms], normally it would be [720ms, 720ms, ...].
When doing a bisect to find the issue, I found this commit to be the cause:
```
7265e603bf880a9ec2cd01c3cf2afbd7709e5af4 is the first bad commit
commit 7265e603bf880a9ec2cd01c3cf2afbd7709e5af4
Author: Vanitha Channaiah <vanitha.channaiah@xxxxxxxxxxxx>
Date: Wed May 15 11:56:33 2019 +0530
pcm: dshare: Added "hw_ptr_alignment" option in configuration for alignment of slave pointers
This change adapt the fix commit 6b058fda9dce
("pcm: dmix: Add option to allow alignment of slave pointers")
for dshare plugin
Issue is that snd_pcm_wait() goes back to waiting because the hw_ptr
is not period aligned. Therefore snd_pcm_wait() will block for a longer
time as required.
With these rcar driver changes the exact position of the dma is returned.
During snd_pcm_start they read hw_ptr as reference, and this hw_ptr
is now not period aligned, and is a little ahead over the period while it
is read. Therefore when the avail is calculated during snd_pcm_wait(),
it is missing the avail_min by a few frames.
An additional option hw_ptr_alignment is provided to dshare configuration,
to allow the user to configure the slave application and hw pointer
alignment at startup
Signed-off-by: Vanitha Channaiah <vanitha.channaiah@xxxxxxxxxxxx>
Signed-off-by: Takashi Iwai <tiwai@xxxxxxx>
src/pcm/pcm_dshare.c | 40 +++++++++++++++++++++++++++++++++++-----
1 file changed, 35 insertions(+), 5 deletions(-)
```
I tried the more recent 1.2.6 with the same issue. I also tried all the "hw_ptr_alignment" options with no success.
cc @VanithaChannaiah @tiwai
Issue URL : https://github.com/alsa-project/alsa-lib/issues/221
Repository URL: https://github.com/alsa-project/alsa-lib
